Game Link Cable
Several Game Boy Color titles had multiplayer capabilities via the Game Link Cable. Some games, including Oracle of Seasons and Oracle of Ages, used the Game Link Cable to communicate between two save files. Players can exchange Magical Rings through the Game Link Cable, as well as send Passwords.
In both Oracle of Seasons and Oracle of Ages, Link can use the Blue Snake found in Vasu Jewelers to trade rings. Additionally, Link can also use the Game Link Cable to do a Fortune Link. When two Game Boy Colors are connected and Link speaks with the Blue Snake to do a Fortune Link, both players will get a Seed Ring.
For the Game Boy Advance, a Game Link Cable was required in order to play Four Swords. Players can use a two-player link cable, or a fourth-player Link cable, as Four Swords is meant for 2-4 players. A Game Boy Advance link cable can also be used to connect a Game Boy Advance to a Nintendo GameCube that has a Game Boy Player attached to it.
Game Link Cable for the Game Boy Advance.